Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
h,w=map(int,input().split())
s=[list(input()) for _ in range(h)]
black=0
for i in range(h):
    black+=s[i].count("#")




from collections import deque
que=deque()
que.append([0,0])
s[0][0]="#"
count=[[0]*w for _ in range(h)]
while que:
    
    x=que.pop()
    dx_dy=[[0,1],[1,0],[0,-1],[-1,0]]
    for k in range(4):
        nx=x[0]+dx_dy[k][0]
        ny=x[1]+dx_dy[k][1]
        if 0<=nx<=h-1 and 0<=ny<=w-1 and s[nx][ny]==".":
            s[nx][ny]="#"
            count[nx][ny]=count[x[0]][x[1]]+1
            que.appendleft([nx,ny])
if s[-1][-1]=="#":
    print(h*w-count[-1][-1]-black-1)
else:
    print(-1)